The present invention relates to a motor vehicle body comprising a body center section, which includes a rear floor and a cross member, and to a motor vehicle comprising such a motor vehicle body.
Motor vehicle bodies, in particular self-supporting motor vehicle bodies, are typically made of steel. Moreover, for bodies having a space frame design, it is known to produce the frame construction from steel or aluminum and to insert plate elements made of plastic material in the frame construction. For example, the published prior art DE 10 2006 052 992 A1 shows a frame structure for the underbody of a motor vehicle body, which includes a center tunnel, a heel plate and lateral sills, which are all part of the frame structure, which is made of high-strength steel. A front floor, which is to say a floor in front of the heel plate, and a rear floor, which is to say a floor behind the heel plate, are made of a plastic material, which is in part reinforced with metal so as to improve crash resistance/strength during impact.
It is now the object of the present invention to create a motor vehicle body comprising a body center section that is lighter in weight and has a required impact resistance.
This object is achieved by a motor vehicle body comprising a body center section that includes a rear floor and a cross member connected thereto, wherein the rear floor and the cross member are made of fiber-reinforced plastic material.
A connection between the rear floor and the cross member can preferably be an adhesive joint, which is to say that the rear floor can be glued to the cross member.
By using fiber-reinforced plastic material for the rear floor and the cross member connected thereto, the body center section is considerably lighter in weight, while meeting the requirements in regard to rigidity of the body center section in normal driving operation, as well as strength and energy absorption capability of the body center section in the event of a side impact/side crash.
According to the present invention, the cross member preferably extends between a left lateral longitudinal beam and a right lateral longitudinal beam in the motor vehicle body.
The rear floor can likewise preferably extend between the left lateral longitudinal beam and the right lateral longitudinal beam.
Moreover, the cross member can be glued to the left lateral longitudinal beam and the right lateral longitudinal beam. The rear floor can likewise preferably be glued to the left lateral longitudinal beam and the right lateral longitudinal beam.
According to one refinement of the present invention, the cross member is disposed between a front floor and the rear floor on the motor vehicle body. An upper end of the cross member can be connected to the rear floor. Moreover, a lower end of the cross member can be connected to the front floor. The connections are preferably designed as adhesive joints.
According to this refinement, the upper end of the cross member can be connected to a top side or a bottom side of the rear floor. To this end, an upper end region of the cross member, which includes the upper end of the cross member, can be designed to overlap a front end region of the rear floor.
The upper end region of the cross member and the front end region of the rear floor together can form a closed hollow section. In the case of a closed hollow section, there are at least two connecting regions, such as glued regions, between the cross member and the rear floor. For example, the front end of the rear floor is then connected in particular to the beginning of the upper end region of the cross member, and the upper end of the cross member is connected to a beginning of the front end region of the rear floor.
If the cross member is joined to the bottom side of the rear floor, the front end region of the rear floor can extend over the upper end region of the cross member and overlap the same.
Conversely, if the cross member is joined to the top side of the rear floor, the front end region of the rear floor can extend over the upper end region of the cross member and overlap the same.
A closed hollow section is more advantageous than an open section in terms of rigidity and strength in many load directions. By utilizing both components, these being the cross member and the rear floor, for the hollow section, only a small number of components are required. A closed section here refers to a section that is closed in a sectional view in the direction of the longitudinal vehicle axis and the vertical vehicle axis.
According to one refinement, the cross member can be formed of a front cross member element and a rear cross member element, which are connected to each other.
The front cross member element and the rear cross member element can overlap each other in an upper region of the cross member. The overlap can be formed in particular in a substantially horizontal region of the cross member. The overlap can extend essentially over the entire upper region of the cross member.
In particular if the upper end region of the cross member overlaps the front end region of the rear floor, the overlap of the front cross member element and of the rear cross member element can be designed above the front end region of the floor. In particular, the overlap of the front cross member element and of the rear cross member element can extend together with the rear floor in a highest region of the cross member.
The overlap in the upper region of the cross member results in a material augmentation in this region and can contribute considerably to flexural strength of the cross member about a longitudinal axis. This increased flexural strength is necessary especially during a side impact.
Instead of an overlap, a higher material thickness can also be used in the upper region of the cross member. This is possible both with a single-piece design of the cross member and with a multi-piece design of the cross member.
Moreover, in an alternative refinement of the present invention, the cross member is joined to a front end region of the rear floor and the rear floor is connected to a front floor in the motor vehicle body. According to this alternative refinement, the cross member in particular preferably forms a closed hollow section together with the front end region of the rear floor.
In this alternative refinement, the cross member can also be composed of at least two cross member elements, such as a front and a rear cross member element, which preferably overlap each other at the connecting point thereof. Likewise, the connecting point can be located in a highest region of the cross member, together with the rear floor.
Moreover, in all refinements, a rear end of a center tunnel is preferably joined to the cross member and/or the rear floor.
The center tunnel can extend over the entire body center section. The center tunnel is a region that spans a gap between a right front floor and a left front floor, for example in the form of an inverted U, and beneath which drive elements and/or energy storage elements can be accommodated.
All the described connections between components are preferably designed as glued joints. As an alternative, other joining techniques or additional joining techniques can be used.
In a motor vehicle body according to the present invention, a primary fiber direction runs in the transverse vehicle direction. In other words, a plurality of fibers of the rear floor and of the cross member are oriented in a transverse vehicle direction.
The rear floor and/or the cross member are preferably composed of multiple unidirectional fiber layers, wherein the fiber orientation of each fiber layer can deviate from the transverse vehicle direction by an angle of up to approximately 45° C. Moreover, the orientation of the fibers of one fiber layer can be offset with respect to the orientation of the fibers of another fiber layer by up to approximately 90°. The fiber orientation of at least one fiber layer can preferably extend in the transverse vehicle direction.
For example, the fiber-reinforced plastic material is composed of at least five fiber layers, wherein the center fiber layer extends in the transverse vehicle direction, and the remaining fiber layers extend at an angle of approximately −45° or +45° with respect to the center fiber layer. For example, the first fiber layer extends at an angle of +45°, the second fiber layer extends at an angle of −45°, the third fiber layer extends at an angle of 0° (which is to say in the transverse vehicle direction), the fourth fiber layer extends at an angle of −45°, and the fifth fiber layer extends at an angle of +45°, relative to the transverse vehicle direction.
Particularly high strength in the transverse direction as well as in directions of the motor vehicle body that deviate slightly therefrom can thus be achieved.
Moreover, the body center section, which is to say essentially the entire body center section, is made of fiber-reinforced plastic material in the motor vehicle body according to the present invention.
The motor vehicle body is preferably self-supporting.
The motor vehicle body, which is to say at least the body center section, is preferably designed in what is known as a monocoque construction, including the rear floor and the cross member, wherein the rear floor and the cross member form parts within the meaning of the monocoque construction.
The body center section extends at least within a region between a front axle and a rear axle of the motor vehicle. In the front region, the body center section starts with a front bulkhead, and in the rear region of the body center section, the body center section ends with a rear partition or at least behind a rear row of seats. The body center section comprises in particular what is known as a passenger cell.
Moreover, the motor vehicle body according to the present invention is preferably a motor vehicle body for a motor vehicle having at least one front seat row and one rear seat row, wherein the rear floor is located beneath the seat surface of the rear seat row.
The fiber-reinforced plastic material is preferably carbon fiber reinforced plastic material (CFRP).
The cross member and the rear floor can be produced by way of a transfer molding process, which is also referred to as a resin transfer molding (RTM) method. In the resin transfer molding process, for example, a semi-finished fiber product is inserted as a preform into a mold. Thereafter, resin is injected into the closed mold, for example. However, it is also possible to use other methods for producing the cross member and the rear floor.
All directional information such as top, bottom, front and back, transverse direction, longitudinal direction and the like refer to a motor vehicle body, of course, as it is installed and used in a motor vehicle during normal operation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
The exemplary embodiments of the present invention are described hereafter in detail.